Power supply system and process including sub-switching element control

1. A power supply system comprising: 1) a high voltage power supply for supplying a power having a high voltage; 2) a main power supply wire connecting to the high voltage power supply; 3) a step down circuit comprising the following operations: a) inputting, by way of the main power supply wire, the power having the high voltage, b) stepping down the thus inputted power having the high voltage, and c) outputting a power having a lowered voltage lower than the high voltage, a first predetermined voltage being defined lower than the lowered voltage stepped down by the step down circuit; 4) a sub-power supply wire connecting the high voltage power supply to an output side of the step down circuit; 5) a voltage sensor for sensing a voltage of the power outputted from the step down circuit; 6) a sub-switching element disposed on the sub-power supply wire; and 7) a controller for controlling the sub-switching element, a) the controller turning off the sub-switching element, when the voltage sensed with the voltage sensor is equal to or higher than the first predetermined voltage; and b) the controller driving the sub-switching element in duty control for stepping down the power having the high voltage to the power having the lowered voltage outputted from the step down circuit, when the voltage sensed with the voltage sensor is lower than the first predetermined voltage.

2. The power supply system as claimed in claim 1 , wherein the power supply system includes a warning section to give a warning to a user, and the controller outputs a signal by referring to the voltage sensed with the voltage sensor, to thereby give the warning to the user.

3. The power supply system as claimed in claim 1 , wherein the power supply system includes a warning section to give a warning to a user, the controller drives the sub-switching element at a predetermined duty ratio, and carries out a diagnosis of a failure of the sub-switching element by referring to the voltage sensed with the voltage sensor, and when the diagnosis determines that the sub-switching element has the failure, the controller outputs a signal to the warning section, to thereby give the warning to the user.

4. The power supply system as claimed in claim 3 , wherein the diagnosis of the sub-switching element is carried out when the power supply system is turned on.

5. The power supply system as claimed in claim 1 , wherein the step down circuit includes a switching element which is so driven in duty control as to change the power having the high voltage to the power having the lowered voltage, the sub-power supply wire connects to an output end of the switching element of the step down circuit, the voltage sensor connects to the sub-power supply wire, the controller controls the main switching element and the sub-switching element by referring to a voltage of the sub-power wire which is sensed with the voltage sensor connecting to the sub-power supply wire, and the step down circuit is a DC-DC converter, the sub-switching element is a transistor, and the switching element is a transistor.

6. A power supply process comprising: 1) supplying, from a high voltage power supply, a power having a high voltage; 2) stepping down the power having the high voltage, the stepping down operation by a step down circuit comprising the following operations: a) inputting, by way of a main power supply wire connecting to the high voltage power supply, the power having the high voltage, b) stepping down the thus inputted power having the high voltage, and c) outputting a power having a lowered voltage lower than the high voltage, a first predetermined voltage being defined lower than the lowered voltage thus stepped down; 3) sensing a voltage of the power outputted from the step down circuit; and 4) controlling a sub-switching element disposed on a sub-power supply wire which connects the high voltage power supply to an output side of the step down circuit, the controlling operation comprising the following operations: a) turning off the sub-switching element, when the voltage thus sensed is equal to or higher than the first predetermined voltage; and b) driving the sub-switching element in duty control for stepping down the power having the high voltage to the power having the lowered voltage outputted from the step down circuit, when the voltage thus sensed is lower than the first predetermined voltage.

7. A power supply system comprising: 1) a supplying means for supplying a power having a high voltage; 2) a first connecting means connecting to the high voltage power supply; 3) a stepping down means comprising the following operations: a) inputting, by way of the first connecting means, the power having the high voltage, b) stepping down the thus inputted power having the high voltage, and c) outputting a power having a lowered voltage lower than the high voltage, a first predetermined voltage being defined lower than the lowered voltage stepped down by the stepping down means; 4) a second connecting means connecting the high voltage power supply to an output side of the stepping down means; 5) a sensing means for sensing a voltage of the power outputted from the stepping down means; 6) a sub-switching means disposed on the second connecting means; and 7) a controlling means for controlling the sub-switching means, a) the controlling means turning off the sub-switching means, when the voltage sensed with the sensing means is equal to or higher than the first predetermined voltage; and b) the controlling means driving the sub-switching means in duty control for stepping down the power having the high voltage to the power having the lowered voltage outputted from the stepping down means, when the voltage sensed with the sensing means is lower than the first predetermined voltage.

8. A power supply system comprising: 1) a high voltage power supply for supplying a power having a high voltage; 2) a main power supply wire connecting to the high voltage power supply; 3) a step down circuit comprising the following operations: a) inputting, by way of the main power supply wire, the power having the high voltage, b) stepping down the thus inputted power having the high voltage, and c) outputting a power having a lowered voltage lower than the high voltage, a first predetermined voltage being defined lower than the lowered voltage stepped down by the step down circuit, a second predetermined voltage being defined higher than the lowered voltage stepped down by the step down circuit; 4) a sub-power supply wire connecting the high voltage power supply to an output side of the step down circuit; 5) a voltage sensor for sensing a voltage of the power outputted from the step down circuit; 6) a main switching element disposed on the main power supply wire; 7) a sub-switching element disposed on the sub-power supply wire; and 8) a controller for controlling the main switching element and the sub-switching element, a) the controller turning on the main switching element while the controller turning off the sub-switching element, when the voltage sensed with the voltage sensor is in both of the following states: i) equal to or lower than the second predetermined voltage, and ii) equal to or higher than the first predetermined voltage; b) the controller driving the main switching element in duty control for stepping down the power having the high voltage to the power having the lowered voltage outputted from the step down circuit, when the voltage sensed with the voltage sensor is higher than the second predetermined voltage; and c) the controller driving the sub-switching element in duty control for stepping down the power having the high voltage to the power having the lowered voltage outputted from the step down circuit, when the voltage sensed with the voltage sensor is lower than the first predetermined voltage.

9. The power supply system as claimed in claim 8 , wherein the power supply system includes a warning section to give a warning to a user, and the controller outputs a signal by referring to the voltage sensed with the voltage sensor, to thereby give the warning to the user.

10. The power supply system as claimed in claim 8 , wherein the power supply system includes a warning section to give a warning to a user, the controller drives the sub-switching element at a predetermined duty ratio, and carries out a diagnosis of a failure of the sub-switching element by referring to the voltage sensed with the voltage sensor, and when the diagnosis determines that the sub-switching element has the failure, the controller outputs a signal to the warning section, to thereby give the warning to the user.

11. The power supply system as claimed in claim 10 , wherein the diagnosis of the sub-switching element is carried out when the power supply system is turned on.

12. The power supply system as claimed in claim 8 , wherein the step down circuit includes a switching element which is so driven in duty control as to change the power having the high voltage to the power having the lowered voltage, the sub-power supply wire connects to an output end of the switching element of the step down circuit, the voltage sensor connects to the sub-power supply wire, the controller controls the main switching element and the sub-switching element by referring to a voltage of the sub-power wire which is sensed with the voltage sensor connecting to the sub-power supply wire, and the step down circuit is a DC-DC converter, the main switching element is a transistor, the sub-switching element is a transistor, and the switching element is a transistor.

13. A power supply system comprising: 1) a high voltage power supply for supplying a power having a high voltage; 2) a main power supply wire connecting to the high voltage power supply; 3) a step down circuit comprising the following operations: a) inputting, by way of the main power supply wire, the power having the high voltage, b) stepping down the thus inputted power having the high voltage, and c) outputting a power having a lowered voltage lower than the high voltage, a first predetermined voltage being defined lower than the lowered voltage stepped down by the step down circuit, a second predetermined voltage being defined higher than the lowered voltage stepped down by the step down circuit; 4) a sub-power supply wire connecting the high voltage power supply to an output side of the step down circuit; 5) a voltage sensor for sensing a voltage of the power outputted from the step down circuit; 6) a main switching element disposed on the main power supply wire; 7) a sub-switching element disposed on the sub-power supply wire; and 8) a controller for controlling the main switching element and the sub-switching element, a) the controller turning on the main switching element while the controller turning off the sub-switching element, when the voltage sensed with the voltage sensor is in both of the following states: i) equal to or lower than the second predetermined voltage, and ii) equal to or higher than the first predetermined voltage; and b) the controller turning off the main switching element while the controller driving the sub-switching element in duty control for stepping down the power having the high voltage to the power having the lowered voltage outputted from the step down circuit, when the voltage sensed with the voltage sensor is in at least one of the following states: i) higher than the second predetermined voltage, and ii) lower than the first predetermined voltage.

14. The power supply system as claimed in claim 13 , wherein the power supply system includes a warning section to give a warning to a user, and the controller outputs a signal by referring to the voltage sensed with the voltage sensor, to thereby give the warning to the user.

15. The power supply system as claimed in claim 13 , wherein the power supply system includes a warning section to give a warning to a user, the controller drives the sub-switching element at a predetermined duty ratio, and carries out a diagnosis of a failure of the sub-switching element by referring to the voltage sensed with the voltage sensor, and when the diagnosis determines that the sub-switching element has the failure, the controller outputs a signal to the warning section, to thereby give the warning to the user.

16. The power supply system as claimed in claim 15 , wherein the diagnosis of the sub-switching element is carried out when the power supply system is turned on.

17. The power supply system as claimed in claim 13 , wherein the step down circuit includes a switching element which is so driven in duty control as to change the power having the high voltage to the power having the lowered voltage, the sub-power supply wire connects to an output end of the switching element of the step down circuit, the voltage sensor connects to the sub-power supply wire, the controller controls the main switching element and the sub-switching element by referring to a voltage of the sub-power wire which is sensed with the voltage sensor connecting to the sub-power supply wire, and the step down circuit is a DC-DC converter, the main switching element is a transistor, the sub-switching element is a transistor, and the switching element is a transistor.

18. A power supply system comprising: 1) a high voltage power supply for supplying a power having a high voltage; 2) a main power supply wire connecting to the high voltage power supply; 3) a step down circuit comprising the following operations: a) inputting, by way of the main power supply wire, the power having the high voltage, b) stepping down the thus inputted power having the high voltage, and c) outputting a power having a lowered voltage lower than the high voltage, a second predetermined voltage being defined higher than the lowered voltage stepped down by the step down circuit; 4) a voltage sensor for sensing a voltage of the power outputted from the step down circuit; 5) a main switching element disposed on the main power supply wire; and 6) a controller for controlling the main switching element, the controller driving the main switching element in duty control for stepping down the power having the high voltage to the power having the lowered voltage outputted from the step down circuit, when the voltage sensed with the voltage sensor is higher than the second predetermined voltage.

19. The power supply system as claimed in claim 18 , wherein the power supply system includes a warning section to give a warning to a user, and the controller outputs a signal by referring to the voltage sensed with the voltage sensor, to thereby give the warning to the user.

20. The power supply system as claimed in claim 18 , wherein the step down circuit is a DC-DC converter, and the main switching element is a transistor.